The present invention relates to a machine with a drive for applying a band around a package which is held together after winding around the band, tensioning said band and joining the band ends, the machine drive having a clutch, whose transmittable torque is adjustable, for metering the band tension exerted on the package and which is located between the drive motor and a sliding device for the band.
Various mechanisms and machines are known for applying one or more bands, tapes or strips with which an open or packaged article, hereinafter called package, is held together. These mechanisms are used for tensioning the band placed around the package, to join the band ends and to separate the band from the supply reel. The mechanisms used for this purpose are either operated manually, or are equipped with a hydraulic, pneumatic or electric drive. Applying the band around the package to be wrapped and the insertion of the band with the necessary overlap of the band ends into the mechanism are carried out manually, the mechanism only carrying out the actual joining process with the prior tensioning of the band. In the known machine, the band is largely automatically placed around the package and tensioned, after which the band ends are joined and separated from the supply reel.
In order that band application can take place automatically, the known machines are provided with a band guide in the form of a yoke or a ring, in whose inner area is positioned the package. The end of the band transported by the machine drive into the band guide is manually or automatically inserted into a joining station located at the bottom of said guide. The band is now tensioned by the drive arranged in the machine and, after reaching the desired band tension, the band ends are joined and the band is cut off the supply reel. Transportation of the band through the band guide and tensioning the band after inserting its end and securing in the joining station are carried out by the same drive, which must be reversible due to the fact that the two band movements are in opposite directions, i.e. the wrapping of the package on the one hand and the tensioning of the band on the other. Reversibility is achieved either by a rotation direction change on the drive motor, or by a reversing path arranged in the drive path.
The invention relates to a drive with a reversing path. Alternately engaged clutches, preferably electromagnetic clutches, are used to ensure that the correct band movement is obtained. In one position of said clutches, the sliding device which moves the band for winding around the package is moved, while in the other position the band which is already wound around the package is tensioned by an oppositely directed movement of the band sliding device.
As different bands are used for tensioning the package, it is necessary to match the band tension to the band on the one hand and to the package on the other. It is therefore obvious to construct the clutch engaged during the tensioning of the band simultaneously as a clutch serving to limit the torque to be transmitted. In the case of electromagnetic clutches, it can be brought about by regulating the energizing voltage, but the precision of the transmission moment setting achieved leaves much to be desired particularly in the case of small transmission moments. This makes it virtually impossible to use very thin bands with a lower permissible band tension, or the packaging of fragile or unstable articles.